A lack of clean air through pollution — and the foliage necessary to filter it out — in urban areas has been linked to bad behavior among 9- to 18-year-olds.

Tiny pollution particles called particulate matter 2.5 (PM2.5), which measure 30 times smaller than a strand of hair, are extremely harmful to your health, especially to developing brains that shape the personalities of young people, a new study from the University of Southern California revealed.

“These tiny, toxic particles creep into your body, affecting your lungs and your heart,” the study’s lead author, Diana Younan, told the USC News. “Studies are beginning to show exposure to various air pollutants also causes inflammation in the brain. PM2.5 is particularly harmful to developing brains because it can damage brain structure and neural networks and, as our study suggests, influence adolescent behaviors.”

The study, published in the Journal of Abnormal Child Psychology, focused on Los Angeles. It saw that with heavy pollution, bad behavior in teenagers was exacerbated by poor parent-child relationships and the parents’ mental and social stress levels.

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“Previous studies by others have shown that early exposure to lead disrupts brain development and increases aggressive behavior and juvenile delinquency,” Younan said. “It’s possible that growing up in places with unhealthy levels of small particles outdoors may have similar negative behavioral outcomes.”

For nine years, beginning when the 682 Los Angeles-based children involved in the study were 9 years old, parents completed a behavioral checklist on their kids every few years. The list was made up of 13 bad behaviors like lying, cheating, stealing, arson, truancy, vandalism and substance abuse.

“If you live in an area with high air pollution, like near a freeway or in a neighborhood with little greenery, try to avoid being outside so much and keep windows closed as much as possible.”

(MARK RALSTON/AFP/Getty Images)

Additionally, 25 air quality monitors were used to gauge pollution levels in Southern California from 2000 to 2014 and to measure the PM2.5 amounts outside the homes of each participant.

The researchers found that about 75% of the kids in the study were breathing air that was polluted beyond the recommended federal levels with some measuring at double that amount. The areas where this was most prevalent were in impoverished neighborhoods, some close to freeways, that lacked greenery. More delinquent behaviors were noted from African American boys in these areas.

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“Poor people, unfortunately, are more likely to live in urban areas in less than ideal neighborhoods,” Younan said. “Many affordable housing developments are built near freeways. Living so close to freeways causes health problems such as asthma and, perhaps, alters teenagers’ brain structures so that they are more likely to engage in delinquent behavior.”

“Both lead and PM2.5 are environmental factors that we can clean up through a concerted intervention effort and policy change,” Younan said. “If you live in an area with high air pollution, like near a freeway or in a neighborhood with little greenery, try to avoid being outside so much and keep windows closed as much as possible when the ambient PM2.5 levels are high.”